As in Patent Document 1, there is a structure of a multiple-polyphase motor that owns multiple groups in one of the AC motor of the group of polyphase that is composed by the invertor driving the polyphase and the polyphase aforesaid. Further, as in Patent Document 2, there is a permanent magnet motor which reduce the cogging torque.
[Patent Literature 1] JPH7-264822A
[Patent Literature 2] JP4476202B